Changes of initial posture and anticipatory postural adjustment in self-paced single forward stepping under psychological pressure.

This study aimed to investigate the influence of psychological pressure on postural preparation in an initial posture phase and an anticipatory postural adjustment (APA) phase of a single forward step adopting an exploratory approach. Fourteen participants performed a single step toward a circular target of diameter 10 cm in a self-paced manner in non-pressure and pressure conditions. They were asked to make the stepping movement as brief as possible and to place their right foot accurately in the landing position on the target. Pressure was induced by the presence of a small audience and a false warning of punishment if the performance did not meet certain criteria. Results showed that subjective state anxiety and heart rate increased under pressure (p < .01). Although no significant change was observed in performance, trunk leaned forward toward the target (p < .05) and the centre of pressure moved forward (p < .05) in the initial posture phase under pressure. Furthermore, the mean and maximal backward force applied to the force platform in the APA phase increased under pressure (p < .01). These findings suggest that pressure altered the initial postural preparation of self-paced single forward stepping and were considered in relation to strategy selection and/or negative emotional response. [ABSTRACT FROM AUTHOR]